This invention relates to herbicidal compositions and methods of use. In particular, this invention relates to herbicidal compositions comprising an herbicidally active thiocarbamate in combination with certain mono-, di- and tri-haloalkylphosphonodithioates, the latter serving to prolong the effectiveness of a single application or multiple applications of the thiocarbamate herbicide in controlling undesired plant growth.
Thiocarbamates are well known in the agricultural art as herbicides useful for weed control in crops such as corn, potatoes, beans, beets, spinach, tobacco, tomatoes, alfalfa, and others. Thiocarbamates are primarily used in pre-emergence application. They have been found to be particularly effective when incorporated into the soil prior to the planting of the crop. As a herbicide, the thiocarbamate is most concentrated immediately after its application. How long thereafter the initial concentration is retained depends in large part on the particular soil used. Thus the rate at which the thiocarbamate herbicide concentration declines following its application tends to vary from one type of soil to the next. This is evident in the observable extent of actual weed control after considerable time has elapsed.
It has now been discovered that the soil persistence of certain herbicidally active thiocarbamates is significantly extended by the incorporation of certain mono-, di- and tri-haloalkylphosphonodithioate compounds, which have insignificant or no herbicidal activity of their own at the rates and under the conditions applied. This improvement in the soil persistence of the thiocarbamate can manifest itself in a variety of ways. Improved soil persistence can be shown by herbicidal efficacy tests, wherein the degree of weed injury is measured after a set period of time following application of the herbicide. In such a test, the extender compound is shown to increase the herbicidal effectiveness of the thiocarbamate by increasing the persistence of the latter in the soil, and thus prolonging its effective life.
It is therefore an object of this invention to increase the soil persistence of thiocarbamate herbicides and thus improve their herbicidal effectiveness.
In particular, this invention relates to a novel herbicidal composition comprising
(a) an herbicidally effective amount of a thiocarbamate having the formula ##STR1## R.sup.1 is C.sub.1 -C.sub.6 alkyl, C.sub.3 -C.sub.6 alkenyl, C.sub.7 -C.sub.9 phenylalkyl, or phenyl and is optionally substituted with one, two, or three halogen atoms, and
R.sup.2 and R.sup.3 are either selected independently from C.sub.1 -C.sub.6 alkyl and C.sub.5 -C.sub.7 cycloalkyl, or combined to form conjointly C.sub.4 -C.sub.7 alkylene; PA1 n is 1, 2 or 3; PA1 R.sup.4 is C.sub.1 -C.sub.4 alkyl; and PA1 R.sup.5 is C.sub.1 -C.sub.6 alkyl or C.sub.2 -C.sub.4 alkenyl. PA1 R.sup.1 is C.sub.1 -C.sub.6 alkyl, C.sub.7 -C.sub.9 phenylalkyl or phenyl; PA1 R.sup.2 and R.sup.3 are either selected independently from C.sub.1 -C.sub.6 alkyl and C.sub.5 -C.sub.7 cycloalkyl or combined to form conjointly C.sub.4 -C.sub.7 alkylene; PA1 X is chloro; PA1 n is 1, 2 or 3; PA1 R.sup.4 is methyl or ethyl; and PA1 R.sup.5 is n-propyl, n-butyl or allyl. PA1 R.sup.1 and R.sup.2 are each independently C.sub.1 -C.sub.6 alkyl; PA1 R.sup.3 is C.sub.1 -C.sub.6 alkyl or C.sub.5 -C.sub.7 cycloalkyl; PA1 X is chloro; PA1 n is 1, 2 or 3; PA1 R.sub.4 is methyl; and PA1 R.sub.5 is n-propyl or n-butyl. PA1 R.sup.1, R.sup.2 and R.sup.3 are each independently C.sub.2 -C.sub.4 alkyl; PA1 X is chloro; PA1 n is 2 or 3; PA1 R.sup.4 is methyl; and PA1 R.sup.5 is n-propyl or n-butyl.
(b) a non-herbicidal extending amount of a mono-, di- or tri-haloalkylphosphonodithioate compound sufficient to extend the soil life of said thiocarbamate, said extender compound having the formula ##STR2## in which X is halo;
In a preferred embodiment of the invention, the compounds above are defined such that
In another preferred embodiment of the invention,
In still another preferred embodiment,
This invention further relates to a method of controlling undesirable vegetation comprising applying the above composition to the locus where control is desired.
The invention further relates to new compounds having the formula ##STR3## in which W is chlorine or bromine and R.sup.5 is C.sub.1 -C.sub.6 alkyl or C.sub.2 -C.sub.4 alkenyl. R.sup.5 is preferably n-propyl, n-butyl or allyl. W is most preferably chlorine.
The invention further relates to a process for preparing the above-disclosed novel compounds. Such process is described below after Example 1.
The terms "alkyl" and "alkenyl" are used herein, unless otherwise specified, in their normal meanings and are intended to include both straight-chain and branched-chain groups.
All carbon atom ranges are intended to be inclusive of their upper and lower limits.
The terms "halogen atom" or "halo" are used to designate fluorine, chlorine, bromine, or iodine atoms, as well as any combination thereof.
The term "herbicide," as used herein, means a compound which adversely controls or modifies the growth of plants. By the term "herbicidally effective amount" is meant an amount of compound which causes an adverse modifying effect upon the growth of plants. By "plants" is meant germinant seeds, emerging seedlings and established vegetation, including roots and above-ground portions. Such adverse controlling or modifying effects include all deviations from natural development, for example, killing, retardation, defoliation, desiccation, regulation, stunting, tillering, stimulation, leaf burn, dwarfing and the like.
The term "non-herbicidal" as used herein means that the extender compound at the rate and in the manner applied has insignificant or no herbicidal activity of its own.
The term "extending amount" describes the amount of extender sufficient to prolong the soil life of the thiocarbamate herbicide.
The phrase "to extend the soil life and said thiocarbamate" is used herein to denote the effect whereby herbicidal effectiveness of the thiocarbamate is maintained over time. An extended soil life can be manifested by a slower rate of decline of weed killing potency.